I have recently installed Fedora 12, after many months of using Fedora 10 (and older releases as well ...).

I now find something very odd happening:

I use 2 other computers and switch between them with a KVM. I have never had any problems with this setup before.

If I remain 'connected' (with the KVM) to the linux machine the gnome screen saver cuts in and the system remains 'as is' until 'woken up' with the mouse or keyboard. However, if I switch to another machine using the KVM, within a short time (maybe even minute or two) the linux machine goes dead. Now it has not crashed, as I can log in from a remote machine and do anything I need from a terminal, but the machine seems not to respond. I can't even use ctrl-alt-fn to switch to a console screen.

I initially tried entering telinit 3 from a remote machine but it made no apparent difference.

However, if after telinit 3 I then killed the Xorg process and later issued a telinit 5 the X server restarted, but with a curious black 'notch' at the top of the screen.

Could it be that when there is no video signal from the monitor that something overflows (which was not happening before)? Is that the meaning of 'EQ overflowing'?

No. That is not the problem. It can run for over 24 hours without anything happening even if the KVM has connected the monitor to another screen. It crashes when the KVM reattaches itself to the linux machine. I have another backtrace which might be useful to those who understand these things: